Abstract

Introduction Remote assessment of real-world physical activity is a potentially important addition in evaluating the effect of therapies on how a patient "feels, functions and survives". Actigraphy, the most used measure of physical activity, is an accepted clinical trial endpoint in pulmonary arterial hypertension (PAH), with use in clinical settings becoming increasingly common. Remote monitoring of actigraphy provides high dimensional, real-world data. Despite this, there are challenges in adopting actigraphy as a clinical endpoint. One potential under-recognised issue is the impact of seasonal variation on data interpretation. This study analysed physical activity and physiological measurements of cardiopulmonary function to assess stability and variability throughout the year. Methods 87 patients with a confirmed diagnosis of PAH were enrolled into the UK National Cohort Study of Idiopathic and Heritable Pulmonary Arterial Hypertension (13/EE/0203), and an insertable cardiac monitor (LinQ, Medtronic) implanted using standard techniques. Remote data was collected via a regulatory approved online portal between November 2018 and October 2023. Physical activity and heart rate parameters were measured from the LinQ device which contains an embedded single axis accelerometer. Results Mean age of the 87 patients was 52.5 (14.9 SD) years and 78% were female. Two (2.5%) patients were World Health Organization functional class 1 and 32 (40%), 40 (50%), 6 (7.5%) were classes 2, 3 and 4 respectively. Average daily physical activity varied during the year ranging from 129.5 min/day to 155.0 min/day (figure 1A). Variation in physical activity was cyclical over multiple years and significantly altered by season with physical activity most limited in winter (136 min), increasing in autumn (141 min) and spring (149 min), and greatest in summer (151 min) (figure 1B). There were no seasonal changes in day or night heart rate and heart rate variability (figure 1A). Conclusions In patients with PAH physical activity varies by season through the calendar year measured by actigraphy, however, physiological measures of cardiopulmonary function are unchanged. This finding has implications for the use of actigraphy as a clinical trial endpoint and when assessing longitudinal activity in clinical practice. Seasonal effects may render data challenging to interpret in both contexts and may require adjustment. Conflict of Interest No conflict of interest